398 AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



1905. It escaped observation by earlier investigators of 

 the disease because of its slenderness and the difficulty 

 experienced in getting it stained. 



The disease syphilis is widely spread among civilized 

 people. It has been known from ancient times. 



Morphology. Treponema pallida is a slender organism 

 less in diameter than 0.5/x and varying in length from 4 to 

 20/x. In this organism the spirals are regular and vary in 

 number from three to forty. The spirals are pointed at 

 the tip, very possibly continued into a minute flagellum 

 When observed in a suitable medium under the microscope, 

 the organism is found to be actively motile. It is probable 

 that in most cases the cells divide by transverse fission, 

 although longitudinal division has been claimed. It does 

 not stain well by the ordinary aniline dyes. It is best 

 observed by use of the Giemas 's stain or by impregnation of 

 the tissues with solution of a silver salt, followed by the use 

 of a developer as in photography. 



Culture. The organism was first secured in pure cul- 

 ture by Noguchi, who succeeded in growing it in medium 

 consisting of a mixture of agar and ascitic fluid into which 

 a bit of living tissue had been dropped. A stab culture of 

 the organism in this medium kept under anaerobic condi- 

 tions leads to the development of a hazy growth along the 

 line of the inoculation, particularly near the tissue at the 

 bottom of the tube. 



Pathogenesis. This organism may always be found in 

 the primary and secondary lesions of syphilis. It is pos- 

 sible to reproduce the disease in other animals by inocula- 

 tion of the proper tissues. In man the primary lesion 

 usually takes the form of a hard chancre, which appears in 

 about three weeks after infection. It usually appears on 

 or near the external genitalia. The organism then invades 

 neighboring lymphatics and causes enlargements of the 

 lymph nodes usually in about six weeks after the appear- 



